Europe must develop its military capabilities along the lines proposed by the EU's French presidency if it is not always to wait for America and Nato to be ready to intervene, David Miliband, the foreign secretary, will say today.

In a speech reflecting on Ireland's no vote in last month's referendum on the Lisbon treaty, he will concede that the "EU lacks a clear mission" and the spreading hostility towards it reflects exasperation with seven years of institutional debate.

But in a controversial passage cleared by Downing Street, Miliband will take on the eurosceptics over defence saying he supports the French president, Nicolas Sarkozy's, proposals on EU defence. Sarkozy has argued for a build-up in European military capability, including EU troops going into conflict zones.

Miliband will say: "What strikes me about the French priorities for their presidency is how closely they tie with our own ambitions for the EU, as set out in our global Europe policy statement last autumn whether on energy and climate change, migration, near neighbourhood policy and the next steps on European defence."

He will also praise the French for saying they are willing to reintegrate into Nato's command structure, and will insist that a stronger European defence policy does not mean Nato stops being the cornerstone of European defence.

But he will add: "As the Balkans wars in the 1990s demonstrated, unless Europe can develop its own capabilities, it will be consigned always to wait impotently until the US and Nato are ready and able to intervene.

"That means a genuine role for the EU in conflict prevention and crisis management whether it is providing the civilian experts - the police trainers, judges, civil servants and aid workers - that are needed alongside the military, or deploying soldiers from national armies in roles where Nato is not engaged." He will highlight the role of EU troops in training Palestinian police in the West Bank, adding "the countries of Europe need to be better at using their hard power."

It is estimated there are 2 million soldiers in the 27 EU countries, and yet only 100,000 of them are equipped to fight.

Miliband will point out that Victoria Nuland, the US ambassador to Nato, welcomed a stronger European defence policy in a speech in February, reversing a decade of American fears that strong European defence would undermine Nato. The US position has been changed by Sarkozy's election because he has agreed to reintegrate France into Nato's command structure as well as send more French troops to Nato's operation in Afghanistan.

Diplomatic sources said they have not yet seen the full details of the French proposals on European defence, and there may yet be tensions. Britain has been nervous of French enthusiasm for a command for EU operations outside Nato.

In the speech, hosted by Progress magazine, Miliband will argue the Irish rejection of the Lisbon treaty has shaken the confidence of EU leaders. He will say the Irish result "cannot be dismissed out of hand and has a message for us. We will not get Europe right if we offer a tin ear to the people."